Twenty-six of those patients developed hemolytic uremic syndrome, a form of kidney failure.
The agency said 197 patients from 35 states have become ill from eating contaminated romaine lettuce or from coming into contact with those who did.
The harvest season in Yuma, Arizona is over, and because of the 21-day shelf life of Romaine lettuce, officials do not believe that any of the tainted vegetables is on store shelves or in people's homes at this point.
The reported strain of E. coli, which produces poisonous substances known as Shiga toxins, can cause severe stomach cramps, bloody diarrhea and vomiting.
It can take a while for case reports to make their way to the federal level from state and local officials, and people often do not die right away from complicated E. coli infections.
"Any immediate risk is gone".
As before, a large percentage, 89%, of people interviewed said they ate romaine lettuce the week before they got sick.
According to the official blog of the U.S. Food and Drug Administration, 11 fields in the Brawley, Calif. area are shown to be original sources of the romaine lettuce. Food is often shipped to central plants from various farms, where it is processed, mixed together, packaged, and redistributed. "However, the FDA is committed to investigating the source of the outbreak and working with industry to help prevent similar events in the future".
They haven't been able yet to trace the affected lettuce back to one particular farm, processor or distributor, FDA authorities said in an update Thursday.
So far, they said, "there isn't a simple or obvious explanation for how this outbreak occurred within the supply chain". Unlike spinach, which is often cooked, romaine - and lettuce in general - is more common as a culprit in E. coli outbreaks because it's eaten raw.
The CDC's May 30 update released on Friday also reveals that 25 more ill people from 13 states were added to the investigation since the last update on May 16.